Continuing studies on the Clostridial proline reductase which has been purified to homogeneity will have as their princpal aims (1) characterization of the covalently bound pyruvate (earlier established by Abeles et al to be the carbonyl cofactor of this enzyme) and determination of its origin and mode of linkage to the protein. (2) To isolate and identify the electron carrier(s) required to link proline reductase to the natural electron donor (DPNH) and the artificial donor, reduced methyl viologen. (3) As a cooperative project with T. C. Stadtman to characterize the selenoprotein of glycine reductase and the selenium-containing moiety of formate dehydrogenase by immunological procedures using antisera prepared against the native clostridial selenoprotein.